fix warning for `std::__shared_counter`
fix warning for `std::__shared_counter`

supress warning for CUDA 10.1 - 10.2:

```
alpaka/vec/Vec.hpp(1040): warning ComputationalRadiationPhysics#2912-D: calling a __host__ function("std::__shared_count<( ::__gnu_cxx::_Lock_policy)2> ::__shared_count") from a __host__ __device__ function("alpaka::dev::DevCpu::DevCpu") is not allowed
```

BenjaminW3/alpaka,BenjaminW3/alpaka